Question

For proteins, why is it less likely to see isolated Beta sheets than isolated alpha helices? Is there entropic or enthalpic arguements to support your answer?

Answer 1

Yes…approximately one-fourth of all amino acids in polypeptides favor alpha- helix conformation. The reason for this phenomenon lies in the stability of this conformation, in comparison to other conformations such as sheet or random coil,, which further depends on the degree of hydrogen bonding within the helical conformation .. In an alpha helix , hydrogen bonds are formed between amide hydrogen of one amino acid residue and carbonyl oxygen of fourth amino acid residue resulting in three to four hydrogen bonds between successive turns of a helix. Other conformations lack such degree of hydrogen bonding within a polypeptide, however, they do show considerable levels of hydrogen bonding between polypeptide chains.

if you find this helpful than please vote me.